Over the past 30 years, as-mined oil sand containing bitumen has been slurried and conditioned at applicants' facilities in two different ways.
In the earlier process, the excavated or ‘as-mined’ oil sand was comminute to conveyable size (e.g. −24 inches) with a roll crusher at the mine site and transported on belt conveyors to a central bitumen extraction plant. Here the pre-crushed oil sand was fed into the front end of a horizontal rotating tumbler. Hot water (e.g. 95° C.) was also added, together with a small amount of caustic. The resulting slurry was cascaded as it advanced through the large tumbler over a period of several minutes. Steam was sparged into the slurry to ensure that it was at a temperature of about 80° C. when it exited the tumbler. During this passage through the tumbler, the slurry was ‘conditioned’. That is, lumps were ablated, bitumen flecks were dispersed into the water phase, the flecks coalesced into small droplets and bitumen droplets contacted and adhered to entrained air bubbles. The emerging conditioned slurry was screened to remove oversize and was then ‘flooded’ or diluted with additional hot water. The resulting diluted slurry was introduced into a gravity separation vessel (referred to as a ‘PSV’). The PSV was a large, cylindrical, open-topped vessel having a conical bottom. During retention in the PSV, buoyant aerated bitumen rose to form a top layer of froth, which was removed. The sand settled, was concentrated in the conical base and was separately removed.
If the oil sand was of acceptable quality (for example if it contained >10% by weight bitumen) and if conditioning was properly carried out, recovery of bitumen in the PSV was in the order of 95% by weight.
Over time, the mine faces moved further from the central extraction plant. New mines were also opened that were distant (for example, 25 kilometers away). In addition the belt conveyors were expensive and difficult to operate.
Through research and testing, it was found that if the oil sand was slurried and pumped through a pipeline for a minimum retention time, it would be conditioned as it traveled therethrough and could be fed directly into a PSV with acceptable resulting bitumen recovery.
This led to the implementation of the second system, which is commonly referred to as the ‘hydrotransport system’. One embodiment, referred to as the ‘Aurora’ facility involves:                Transporting the as-mined oil sand using large trucks to a primary crushing facility on the mine site, where the as-mined ore is dumped into a hopper;        The as-mined oil sand is removed from the hopper by a bottom apron feeder, fed into a primary roll crusher and comminuted to conveyable size. The ‘pre-crushed’ oil sand then drops onto a collecting belt conveyor that transfers the ore to a surge bin where an active storage capacity of up to 6000 tonnes can be retained;        An apron feeder transfers the pre-crushed oil sand from the bottom outlet of the surge bin to a belt conveyor which delivers it to the top end of a ‘slurry preparation tower’;        The slurry preparation tower comprises a vertically stacked series of components, aligned to provide a gravity assisted feed through the stack. More particularly the tower comprises, from the top down, a mixing box, vibrating screens and a primary pump box. Water is added to the dry pre-crushed oil sand being fed from the lift belt conveyor to the mixing box. The oil sand and water mix and form a slurry as they proceed downwardly through the overlapping, downwardly inclined, zig-zag arrangement of shelves of the mixing box. The resulting slurry is wet screened to remove oversize, while the remaining slurry passes through the screen and into the pump box. The rejected oversize is comminuted in an impact crusher, water is added and the mixture is fed to a secondary mixing box. The slurry formed in the secondary mixing box is screened by passage through secondary screens to remove residual oversize and the undersize slurry is delivered into a secondary pump box. The oversize reject is hauled away by trucks to a discard area. The slurry in the secondary pump box is pumped back to the primary pump box; and        The slurry in the primary pump box is then transported from the mine site to the central bitumen extraction plant through a pump and pipeline system, wherein conditioning takes place.        
There are some problems associated with the Aurora facility. For example:                The throughput of oil sand is about 8000 tonnes/hour. The facility in its present form is massive. It has a length of 270 meters. The approximate weights of the surge bin, lift conveyor and tower are 2500 tonnes, 750 tonnes and 3100 tonnes respectively. The components do not lend themselves to being relocatable. As the mine faces move away from the slurry preparation tower, the truck haulage distance increases, requiring more trucks. As a consequence, the haulage cost escalates;        Since the slurry preparation system is tied into a pipeline equipped with slurry pumps, there is a need to limit the size of slurry particles to a maximum of about 8 inches. Otherwise stated, the solids in the slurry need to be sized so as to be pumpable. The Aurora design therefore incorporates wet screening for the purpose of removing oversize. However, this leads to the production of oversize rejects and the need for equipment to treat the rejects for recycling;        These oversize rejects can amount to 3% of the original oil sand. There is a bitumen loss associated with the final rejects and it is expensive to haul them to a disposal area; and        The dry ore surge bin is four sided, with twin bottom outlets feeding the apron feeder. A frequently encountered problem at Aurora is that tacky bitumen-rich oil sand has a tendency to plug the bin outlets and it is then necessary to apply air permeation to assist flow.        